BPAL-crotch is a term coined by Agent Foxglove to refer to instances of purple prose during lemon fics which describe a character's bodily fluids as smelling or tasting of things of which they really shouldn't smell or taste. Common descriptions include honey, chocolate, strawberries, champagne, or, in extreme cases, sunshine.
Named for the Black Phoenix Alchemy Lab, a very popular online perfumery known for elaborate descriptions of its scents which range from poetic to urple. The PPC are not affiliated with them, and they do not really deserve to be compared to bad fanfic.